Hydroelectric power generating systems that utilize a water turbine to convert the energy of flowing water into mechanical energy for producing electric energy have been known. Conventional systems are built as water passes through a dam, and into a river below to place the water turbine in the dam for flow of water therethrough. Rivers generate large kinetic energy due to a high head drop when water flowing downward a hillside. It is desired to provide a hydroelectric power generating apparatus that can use the natural downward flow of rivers along a hillside to capture the kinetic energy carried by the river water.